Telegraph transmitting system



w. FRANKLIN 72 TELEGRAPH TRANSMITTING SYSTE Filed Aug. 25, 1936 INVENTOR L.W. FRANKLIN A TORNEY Patented Oct. 8, 1940 PAENT OFFICE TELEGH TRANSMITTING SYSTEM Lawrence W. Franklin, Hasbrouck Heights, N. J.,

assignor to The Western Union Telegraph Company, New York, N. Yr, a corporation of New York Application August 25, 1936, Serial No. 97,826

8 Claims.

This invention relates to telegraph transmitting or keying systems and more particularly to high speed signalling systems requiring relatively large currents, as for example systems employing a large number of receiving instruments operated by a single transmitting device.

An important application of the invention is in quotation systems where a large number of tickers are controlled from a single point. The current consumption of each receiving ticker is relatively high and in practise, where electromagnetic relays are employed for transmitting quotation signals to a number of such tickers, a series of parallel relays must be utilized in order to avoid destructive arcing at the contacts of the relays. The maintenance of the transmitting relays in proper operating condition in order to avoid loss or mutilation of signals presents a problem which becomes increasingly difiicult as the number of tickers in the system increases since the relays must be connected in cascade relation, a group of relays being connected to the contacts of each relay of the preceding group. Obviously, it is desirable to reduce or eliminate 25 the maintenance required in operating systems of this kind, as well as to minimize loss or distortion of signals as a result of contact troubles, et cetera. Furthermore, the relays suitable for this service are expensive, requiring a large ini- 30 tial investment in addition to the maintenance charges, and take up considerable floor or rack space.

In general terms, it is the object of the present invention to provide a keying system that over- 5 comes these disadvantages and limitations of the relay system, and is adapted to transmit signals to any desired number of receiving instruments at a high rate of speed without substantial distortion.

A further object of the invention is to provide an improved keying system employing electric discharge devices or valves, such as gaseous or vapor tubes of the discontinuous control type.

A further object of the invention is to provide a signalling system employing electric discharge devices for keying or repeating signals and in which the number of receiving instruments may be increased as the system is extended by the installation of additional parallel discharge devices to take care of the additional load on the system without substantial change in the initial installation.

A still further object of the invention is to provide a system of the character described which is not damaged by the grounding'of a line circuit and remains operative even though one of the discharge devices or tubes fails or is worn out.

Other objects and advantages of the invention will become apparent from the following description of the preferred embodiments thereof shown in the accompanying drawing.

The invention is illustrated as applied to a quotation system in which a number of receiving instruments, such as tickers, are controlled by a single transmitter although the invention is not limited to such systems. In systems of this character, the tickers may be high-speed printer units responsive to six-unit permutation code signals similar in construction to that shown in Letters Patent #1,916,168 to Dirkes and Wheeler, dated June 27, 1933, and assigned to The Western Union Telegraph Company. The transmitting equipment embodying the invention may be arranged to send marking and spacing signals of opposite polarity or signals consisting of current and nocurrent intervals.

In accordance with a preferred embodiment of the invention, a source of alternating current is employed having a frequency at least three or four times the signal frequency, 1. e., 500 or 1000 cycles a second or more. The alternating-cur: rent source is connected to the transmitting circuit or circuits through gaseous or vapor electric discharge devices or valves controlled by a tape transmitter or other suitable code transmitter. The discharge devices employed are commonly termed discontinuous control tubes since they are rendered conductive by the application of potential to a grid or igniter electrode which is thereafter incapable of affecting the discharge as in the case of vacuum or low pressure discharge tubes in which negligible gas ionization occurs. The use of gaseous tubes, however, has the advantage that relatively large currents may be passed through the tubes with a small voltage drop and consequently a low power consumption. The construction and operating characteristics of such gaseous discharge tubes are well known to those skilled in the art.

The discharge devices or valves are thus operative to key the circuits to a large number of tickers in response to control currents of small magnitude derived from the tape transmitter. Each valve is so connected to the alternatingcurrent source that the anode thereof alternately becomes positive and negative with respect to the cathode and, since the device becomes nonconducting' when the anode is negative, the discharge current ceases during each alternate halfcycle and is not re-established unless the control electrode is maintained at such potential that the device breaks down upon the next half-cycle. In this manner the signalling current impressed upon the line, the magnitude of which may be increased to any desired extent by merely increasing the size of the discharge devices, is stopped and started in accordance with the operation of the tape transmitter. If desired, a plurality of discharge devices may be operated in parallel so that if one tube fails, the load current is divided between the remaining tubes and the system continues to function properly. As the number of tickers connected to the system increases as new subscribers are obtained, additional tubes may be added without alteration of the existing apparatus.

Two modifications of the invention are illustrated by way of example in the accompanying drawing, in which- Fig. l is a circuit diagram of a quotation system employing signals consisting of current impulses separated by no-current intervals Fig. 2 is a circuit diagram of a similar system employing signalling impulses of opposite polarity; and

Figs. 3 and 4 are diagrams illustrating the signals transmitted in the systems shown in Figs. 1 and 2, respectively.

Referring to Fig. l of the drawings, I have shown a permutation code transmitter l0 arranged to control a transmitting relay I! in accordance with code combinations to be transmitted over line circuits I2, l3 and Hi extending to a plurality of tickers l5. Any desired number 7 of receiving instruments may be connected to the transmitting apparatus and each line circuit may include two or more tickers in series relation. Furthermore, the invention may be employed in connection with various types of controlling and receiving apparatus in electrical signalling systems known in the art although it is of particular value in connection with high speed code telegraph systems employing short current impulses transmitted in rapid succession. As shown, the transmitter H] is similar to that disclosed in Letters Patent #1305374 granted to Rothermel, May 12, 1931, and assigned to The Western Union Telegraph Company. The transmitter comprises a tape transmitter unit 20 having a plurality of selectively operable contacts 2| connected to a series of feeler pins 22 to be positioned in accordance with the perforations in a tape 23; and a distributor having contacts 24 connected to the respective contacts of the tape transmitter 20 and an operating cam 25 for closing the contacts of the distributor in succession to transmit to the relay H the signal combination set up in the tape 23. The tape may be prepared in the usual manner and the detailed construction and operation of the distributor transmitter is fully set forth in the above-mentioned Rothermel patent.

The relay H is arranged to key the output currents of two gasor vapor-filled discharge devices 30 and 3! connected in the transmitting circuit 32. Each of the discharge devices is of the discontinuous control type and, when conductive, the devices are adapted to apply signalling currents of the desired magnitude to the transmitting circuit 32 from alternating-current sources represented by the two halves of the secondary winding 33 of a transformer 34. The transformer 34 is connected to an alternatingcurrent source of suitable frequency, for example, 1000 cycles per second. The sources of ourrent connected to the discharge devices 30 and 3| may be of any desired character, out of phase and of a frequency at least three or four times the signal frequency.

The discharge device 38 comprises a cathode 31, anode 38 and control electrode 33 adapted to control the conductivity of the discharge device. For example, the control electrode may maintain the device 30 non-conductive at a certain potential whereas when the control electrode becomes less negative or more positive, a discharge occurs between the cathode 31 and anode 38 during each half-cycle of the voltage impressed thereon by the transformer 34 when the anode is positive with respect to the cathode. The discharge device 3| is similar to the discharge device 30 and comprises a cathode 4|, anode 32 and control electrode 43 sealed in an envelope containing a filling of gas, mercury vapor or the like.

The cathodes 31 and 4| are connected to the transmitting circuit 32 and the anodes 38 and 42 are connected to the terminals of the secondary winding 33 of the transformer 3 the midpoint of which is grounded. The control electrodes 39 and 43 are connected through a resistor 46 and battery 4'! to the cathodes of the discharge devices 30 and 3|; and when the contacts of relay H are closed, said control electrodes are connected through a resistor 48, the contacts of relay H and battery 49 to said cathodes 3'! and 4|. As shown, the polarities of the batteries 4'! and 49 are such that when the contacts of relay II are open, the potential impressed upon the control electrodes 39 and 43 maintains the discharge devices or valves 3!) and 3| non-conductive whereas the control electrodes become positive or less negative when the contacts of relay close and the discharge devices become conductive. Thus when the relay closes its contacts, signalling current is impressed upon the transmitting circuit 32 from the transformer 34. Since the discharge devices 30 and 3| only conduct current when the anode of either device is positive with respect to its cathode, it will be apparent that each device is conductive during alternate half-cycles during the periods when the contacts of relay are closed, and when the contacts of relay open, the discharge current through the valve that happens to be conducting current ceases as the voltage wave passes through zero and is prevented from re-striking during the next cycle by the potential of the control electrode derived from the battery 41.

Thus although the discharge devices or valves 30 and 3| are of the discontinuous control type in which the potential of the control electrode is not effective to alter the discharge current through the device after it becomes conductive, by the use of an alternating current of a frequency of 1000 cycles per second or more, the signalling impulses impressed upon the line circuit correspond closely in shape to those generated by the transmitter l0. In certain applications and particularly where the signalling fre quency is low, a power source of a lower frequency, such as 500 cycles per second, may be employed.

The signalling impulses obtained in a high speed ticker system employing a 1000-cycle power source are shown in Fig. 3, Fig. 3a representing the square-topped printer signals impressed upon the relay H and Fig. 3?) representing the corresponding. line signals. In order to decrease the amplitude of the current variation resulting from the use of an alternating-current source, a lowpass filter comprising a series inductance 50 and shunt condensers i may be connected in the transmitting circuit 32, as shown in Fig. 1. Fuses 52 may also be connected in each branch of the transmission circuits to disconnect any branch circuit that accidentally becomes grounded.

Instead of employing spacing signals consisting of no-current intervals, the system may be arranged to transmit marking signals of one polarity and spacing signals of the opposite polarity. This modification is illustrated in Fig. 2 and, as shown, the system comprises a transmitter in of the type shown in Fig. 1 arranged to control a transmitting relay 54. The armature of the relay '54 is connected through a resistor 55 to positive battery and the respective contacts cooperating with said armature are connected to two groups of discharge devices arranged to impress signalling impulses of opposite polarity upon the line circuit 56. The discharge devices 66, 6|, 62 and 63 of one group have their control electrodes connected in parallel relation to one contact of the relay 54 and the other contact of said relay is connected to the control electrodes of the other group of discharge devices 64, 65, 66 and 67. Alternating-current means including a transformer H having two secondary windings i2 and H3 are provided for energizing the line circuit 56 through one or the other of said groups of discharge devices depending upon the position of the armature of relay 54. The windings l2 and 73 may be similar and the peak voltage across one-half of one of said windings should be smaller than the positive voltage impressed on the resistor 55. I

The discharge devices or valves 6ll6l may be similar in construction and operating characteristics to the devices 36 and 3| described above in connection with the system shown in Fig. 1. The anodes of valves 66 and 62 are connected to one terminal of the secondary winding l2 of transformer H and the anodes of valves 6| and 63 are connected to the other terminal of said winding. The anodes of valves 64, 65, 66 and 61 are similarly connected to the terminals of the secondary winding 13 of transformer TI." The valves 62, 63, 66 and '6'! may be omitted if desired, being connected in parallel to the valves 60, 6 I, 64 and 65, respectively, or additional valves may be employed in similar relation to increase the capacity of the system as the load increases. If the valves are operated in parallel, as shown, resistors 15 are preferably connected in series relation with the anode circuit of each valve to insure proper division of the load current.

The control electrodes of the discharge devices Bil-63 connected to the left hand contact of relay 54 and the control electrodes of the discharge devices 6461 are connected to the right hand contact of said relay whereby the two valve groups are alternately rendered conductive as the relay armature engages first one and then the other contact. When the relay armature is in engagement with the left hand contact, as shown, the control electrodes of valves 64--61 are biased to such a potential by a battery 18 that the valves are non-conducting. A battery is associated with the first groupof valves is provided to maintain said valves non-conducting while the relay armature of relay 54 is in engagement with its right hand contact. Thus the line circuit 56 is energized through one group of valves while the armature of relay 54 is in engagement with its marking contact and said circuit is energized through the other group while the armature of. said relay is in engagement with its spacing contact.

In order to reverse the signalling current in the line as the groups of valves are alternately rendered conductive, the valve groups are oppositely connected between the transformer windings and the line circuit. The midpoint of the winding '82 is connected to the line circuit and the cathodes of the associated valve group 6il63 are grounded Whereas the cathodes of the other valve group are connected to the line circuit and the midpoint of the winding H3 is grounded. The discharge current through the conductive group of valves is interrupted as the armature of relay 55 moves from one contact to the other since the potential impressed upon each valve of each group drops to zero during each cycle of the alternating voltage derived from transformer H. In order to protect the valves against excessive current flow, fuses 8! may be connected in series relation with each valve. If one of the fuses 30 or the associated valve becomes burnt out, the load will be assumed by the: parallel valve and the system will remain operative.

In this manner, current impulses of opposite polarity corresponding to the marking and spacing impulses received by relay 55- are impressed upon the line circuit. Fig. 4a represents the transmitter signals and Fig. 4b the signals impressed upon the line to operate receiving instruments or tickers 85. A lamp 86 may be connected in series relation with each branch conductor or circuit whereby the excessive current drawn by a circuit which accidentally becomes grounded will light the lamp in series with the grounded circuit to indicate the abnormal circuit condition. The resistance of each lamp 86 also. prevents a defective branch circuit from grounding the entire system so that the remaining circuits are not aifected by the accidental grounding of one branch line.

It is obvious that various modifications of the systems shown and described in detail for the purpose of explaining the invention will occur to those skilled in the art and consequently I desire that the invention shall not be limited in scope except as indicated in the appended claims.

I claim:

1. A signalling system comprising a line circuit, a plurality of recorders responsive to current impulses connected to said line circuit, means including a discharge device of the discontinuous control type in said circuit for transmitting signals consisting of successive current impulses over the circuit, said discharge device embodying a control electrode, means for normally maintaining the potential of said control electrode at a predetermined value, an alternating-current source in series with said discharge device and the line circuit, the frequency of said source being relatively high compared with the maximum signal frequency, and means including a source of periodic signals for varying the potential of said control electrode of the discharge device to control the conductivity of said device and thereby produce current impulses in the line circuit to operate said recorders.

2. A signalling system comprising a plurality of line circuits, means including a discharge device of the discontinuous control type in said circuits for transmitting signals consisting of successive current impulses over the circuits, an alternating-current source in series with said discharge device and line circuits, the frequency of said source being relatively high compared with the signal frequency and means including a source of periodic signals for rendering said discharge device conductive, whereby said seriesconnected alternating current source and discharge device impress rectified current signals on said line circuit corresponding to the signals generated by said source of periodic signals.

3. A signalling system comprising a line circuit, a plurality of recorders responsive to periodic current impulses connected to said line circuit, two oppositely connected discharge devices of the discontinuous control type in said circuit, said discharge device embodying control electrodes, a transmitting contact device, means including said contact device for varying the potentials of said control electrodes for controlling the conductivity of said devices in accordance with periodic signals to be impressed upon the line circuit and alternating-current means in series with the discharge devices for energizing said line circuit through said discharge devices, the frequency of said alternating-current means being relatively high compared with the signal frequency.

4. A signalling system for operating a number of high speed telegraph recorders comprising a line circuit, two oppositely connected discharge devices of the discontinuous control type in said circuit, means for controlling the conductivity of said devices in accordance with periodic signals to be impressed upon the line circuit and alternating-current means of a frequency of the order of 10% cycles per second in series with said discharge devices for energizing the line circuit alternately through one or the other of said discharge devices.

5. A signalling system comprising a plurality of parallel line circuits, a discharge device of the discontinuous control type, said device including a cathode, anode and control electrode, alternating-current means for energizing the line circuits through said discharge device when the latter is conductive, means including a source of periodic signals connected to vary the potential of the control electrode of said discharge device for rendering the discharge device conductive in predetermined relation to said signals and a source of potential connected to said control electrode to maintain said discharge device non-conductive except upon the occurrence of said signals.

6. A signalling system comprising a plurality of telegraph recorders, a line circuit thereto, a plurality of discharge devices of the discontinuous control type connected in parallel relation in said circuit, a plurality of other discharge devices of the discontinuous control type connected in parallel relation in said circuit and adapted to conduct current in the opposite direction, a resistor in series relation with each of said discharge devices, alternating-current means for energizing the line circuit through said discharge devices and means for controlling the conductivity of said discharge devices in accordance With signals to be impressed upon the line circuit.

7. A signalling system comprising a plurality of telegraph recorders, a line circuit thereto, a plurality of discharge devices of the discontinuous control type connected in parallel relation in said circuit, a plurality of other discharge devices of the discontinuous control type connected in parallel relation in said circuit and adapted to conduct current in the opposite direction, a resistor in series relation with each of said discharge devices, means for controlling the conductivity of said discharge devices in accordance with signals to be impressed upon the line circuit and separate alternating-current sources of opposite phase connected to the line circuit through the respective groups of discharge devices.

8. A signalling system comprising a line circuit, an alternating-current transformer provided with two secondary windings, electric valve means of the discontinuous control type for impressing signalling current of one polarity from one of said windings upon the line circuit and signalling current of the opposite polarity from the other of said windings upon the line circuit, means for controlling said valve means in accordance with predetermined code signals to generate current impulses of opposite polarity in the line circuit and telegraph receivers connected to said line circuit.

LAWRENCE W. FRANKLIN. 

